1. Field of the Invention
The present invention relates generally to systems and methods for pipeline rehabilitation, and, more specifically, the present invention relates to devices used to cut or assist in the cutting of lateral openings in a main pipeline after a relining process.
2. Description of the Background
Various pipeline networks are used in a variety of different technological disciplines. For example, largely subterranean potable water pipeline networks deliver clean water to homes and businesses and sewer pipeline networks guide used water and wastes away from these same locations for further treatment or disposal. In general, pipeline networks are used to guide an almost limitless variety of liquids and gases from one location to another, either under pressure or by the force of gravity.
A section of a conventional pipeline network for subterranean sewers is shown in FIG. 1. FIG. 1A shows an isometric view of the pipeline network, and FIGS. 1B and 1C show front (down the longitudinal axis) and side views, respectively. As seen in FIG. 1, a main line 10 typically traverses in a longitudinal direction with a variety of different lateral lines 12, 14 intersecting the main 10 at various locations. The lateral connections with the main 10 occur at various angles in planes co-linear with the longitudinal axis (FIG. 1C) and perpendicular to the longitudinal axis (FIG. 1B). A lateral typically may intersect with the main 10 at any angle within the upper hemisphere of the main.
The pipeline network also includes a plurality of surface manholes (not shown) that provide access to the subterranean pipeline network at various locations. For sewer pipelines, a distance of 300 feet between successive manhole access points is common. These access points intersect with the main as vertically intersecting laterals.
After years of wear, the walls of the pipelines begin to crack, leak and generally deteriorate, and this wear may adversely affect use of the pipe. As such, various processes have been developed to rehabilitate these pipelines and provide for a longer service life. One common rehabilitation method involves relining the interior walls of pipes with an epoxy or resin-impregnated felt liner that is prefabricated and rolled in the form of a rolled-up sock (i.e., one end open and one end closed). The liner is fed down through a manhole access point and is guided into the pipeline main. Pressurized water is then forced into the open end of the rolled liner forcing it to unroll and unfurl down the length of the main. The far end of the liner is tied off or closed to allow for the expansion of the felt liner against the inside of the pipe wall.
The relining process is typically performed on pipes that have been prepared for relining by removing serious flaws, such as collapses and extensive debris. In these cases, a machine or other means, depending on the size of the pipe, is used to assess and repair the main and/or lateral (extending to a house or building) before relining.
After unrolling, the felt liner, often referred to as Cured In Place Pipe (CIPP), is filled with pressurized heated water and is allowed to cure for several hours depending on the CIPP length, thickness and other relining factors. For an 8″ sewer main, a typical cure time may be three hours. After curing, the closed end of the liner is cut open allowing the water to proceed down the main out of the liner. The result is a relined, and hence rehabilitated, pipe that lasts for up to 50 more years with regular maintenance. This process is obviously much cheaper than excavating and replacing the mains of subterranean pipe networks.
At this point, each of the lateral connections with the main is now covered over with the cured epoxy lining. Therefore, to restore service to the houses and other buildings connected to the main through the laterals, new openings in the Cured In Place Pipe must be cut at each lateral connection. Typically, for smaller pipes that do not allow for man-entry within the mains for cutting (e.g., smaller than 24″ in diameter), a small tele-operated machine is used to cut the laterals open after curing. The machine includes an air-powered routing bit with three axes of manipulation that is tele-operated from the surface. Via tele-operation, the cutting machine is positioned in front of a lateral.
To accomplish the lateral cutting task using conventional methods, the operator uses a camera view from an inspection sled which is being towed directly in front of the lateral cutting machine which provides a perspective view of the cutting operation. Typically, a conventional video feed is used for tele-operation of the machine. The operator (at the surface) uses the analog video image to look for a “dimple” or depression in the newly cured liner caused by the pressurized water indenting the soft felt liner at the location of most laterals. In some cases, a lateral may not cause a dimple in the liner. In these cases, a pay-out sensor may be used to generally identify the location of each lateral prior to lining, and the lateral cutting machine may be stopped at each of the recorded locations after lining and attempt to drill or punch a lateral hole at each of these locations. In either case, the conventional method lacks a great deal of precision.
Once the lateral locations are found, the operator uses his camera view to punch through the lined lateral and relieve any backpressure in the lateral pipe (e.g., so that waste water does not back up all the way into the house or building). Then, the operator must re-cut the opening of the lateral to some predefined standard (e.g., 90–95% of the original diameter of the main-lateral interconnection). Further, it is important that the cutting step not leave a ledge at the lower portion of the lateral as such a ledge would provide a collection point for waste and other materials that may come down the lateral in the future.
In all, conventional lateral cutting machines, even with an experienced operator, take approximately 30 minutes to cut each lateral open after relining. This process is performed serially, one lateral at a time. In a typical 300 foot sewer run, there may be 15 laterals which would take 7½ hours to cut. This, combined with the setup, inspection and breakdown time, can total over 9 hours just to reestablish service to a single section of main sewer pipes. Even if the relined pipe lasts for 50–70 years as projected, upkeep on the millions of miles of underground sewer and potable water pipe in this country would be beyond the scope of conventional methods.
Although shown and described herein with respect to sewer pipelines, the present invention could also be used in other industries, such as general industrial, water, gas, or chemical pipes. Those skilled in the art can easily adapt the features of the present invention to these and other pipeline networks.